Can't connect to my wireless network though GNOME

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I am a complete Linux beginner and I managed to install Archlinux today. But I have no access to my wifi for some reason.
I get internet access in my terminal with wifi-menu but gnome tells me that it can not connect to my wireless network. The password is 100% correct.
I followed this guide and installed network-manager-applet, and I also changed the rc.conf file:
rc.d start networkmanager
I also installed pacman -S networkmanager
I restarted networkmanager, enabled / disabled it, started it again. I also turned the wireless network in GNOME on and off. But nothing helped.
Any ideas w
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